1. Field of the Invention
The present invention is directed to conveyor belts, and in particular, to modular and grid style conveyor belts. The present invention is further directed to methods for assembling such conveyor belts.
2. Description of Related Art
Conveyor systems are commonly used in various industrial fields for material handling and processing purposes. For instance, conveyor systems are used in food processing systems in which food items are placed on the support surface of a conveyor belt and processed, while being conveyed from one location to another. In such applications, the food items may be cooked, baked, frozen, washed, or subject to other processing steps while being conveyed on the conveyor belt. Various different types of conveyor belts have been used such as wire mesh conveyor belts. Modular belts have become especially popular in food processing systems. Moreover, conveyor systems are often used in a helical accumulator such as that disclosed in U.S. Pat. No. 5,070,999 to Layne et al. which allows storage of a large number of items in the conveyor system.
Many modular conveyor belts include a plurality of link elements, each link element having a plurality of spaced intermeshing extensions that intermesh with extensions of adjacent link elements. The intermeshed link elements are hingeably interconnected together by elongated pivot rods so as to form a continuous conveyor belt, the plurality of link elements providing the conveying surface. The link elements are generally made of a non-metallic material such as plastic, nylon, or other composite materials. The use of such link elements have become popular especially in food processing applications because the conveyance surfaces are easy to clean, and can be treated to resist growth of pathogens such as germs, fingus, viruses and bacteria.
Modular conveyor belts typically rely on an arrangement of modules such that one module arranged with one pitch, is intermeshed with the ends of two abutted modules arranged with a second pitch, in effect joining them to prevent lateral motion of the two abutted modules with respect to each other. This arrangement is repeated at a sufficient number of joints to create a continuous connection between both edges of the conveyor belt, and provide the interconnectivity that holds the opposite edges of the conveyor belt together. The practice of overlapping modules in adjacent pitches is similar to the technique of laying bricks in an overlapping pattern. Therefore, this arrangement of modules is commonly referred to as a brick-laid pattern. The rod typically does not prevent lateral movement of the links other than by joining together the modules. In many cases, the rod has no head or retention features, and is merely trapped by retention features at both edges of the conveyor belt. Examples of conveyor belts having such an arrangement are disclosed in U.S. Pat. Nos. 5,105,938, 5,156,264, 5,598,916 or U.S. Pat. No. 6,644,466. In some cases two separate rods may be inserted from both sides and snap into the outer edge extensions to prevent escape. However, even in such configuration, brick-laid modules are still required because there is not a continuous rod connecting the edges.
For typical modular conveyor belts, some portion of the modules must be integrally formed with the links to facilitate brick-laying, and therefore, there is little or no flexibility in the selection of overlay patterns or materials without significant investment in new link tooling. In some applications, the links are formed separately, and are configured to mechanically join to the modules to produce the same brick-laying ability as integrally formed links and modules. However, a limitation of such configuration is that it produces undesirable crevices that can harbor pathogens if used for conveying food items.
Grid style conveyor belts typically include intermeshing U-shaped links at both edges of the conveyor belt which are hingeably connected by pivot rods. The pivot rods traverse the width of the conveyor belt, connecting the links at opposite sides and forming the conveying surface. In some cases the surface is modified with metal or plastic overlay to improve product support. Grid style conveyor belts are typically constructed of metal links welded to metal rods. Since the links are joined to the rods in a manner that prevents lateral motion of the link with respect to the rod, brick-laid center modules are not required to maintain the integrity of the belt. However, this type of construction requires cutting, grinding, and welding to separate, join, or repair the belt. In food processing facilities, cleaning and sanitation of the belt is required following repairs of this nature.
Various modular conveyor belts are known in which pivot rods are inserted into intermeshed link elements, the rods being retained by a feature provided on the link elements. For example, U.S. Pat. No. 5,105,938 to Tan noted above discloses a conveyor belt having links that are interdigited and pivotably connected by rods, a belt link end having an aperture with an occlusion to retain the pivot rod in place at one of two bi-stable positions. The patent to Tan discloses a substantially round exit-entrance aperture, and a ridge or waist resiliently formed for holding the pivot rod. However, this patent requires the rods to be moved over the ridge by deforming the ridge which can weaken the links. In addition, inadvertent removal of the rods can occur.
U.S. Pat. No. 5,598,916 to Horton et al. noted above discloses a modular conveyor belt similar to that disclosed above with respect to Tan, except that the modular conveyor belt links of this reference does not include a ridge. The aperture provided on the belt links allows installation and removal of the rod. However, the aperture is offset relative to the rod receiving aperture of the links thereby requiring the insertion of the pivot rods at an angle, or alternatively, requiring the use of a bendable pivot rod, both of these requirements being undesirable.
U.S. Pat. No. 6,644,466 to Knott et al. noted above discloses a platform top radius belt in which the modules include protrusions that extend to support an end of the pivot rod, the protrusion fitting between a projecting portion and a narrow hinge element. This patent discloses that the protrusion includes a notch so as to allow the pivot rod to be inserted into the apertures of the hinge elements. However, the belt disclosed in Knott et al. also does not prevent unintentional removal of the rod.
U.S. Pat. No. 5,156,264 to Lapeyre noted above discloses a pivot rod retention apparatus for conveyor belts including stop members provided on a link. The stop members are displaced during the insertion of the pivot rod, and return to position to retain the pivot rod thereby preventing transverse movement of the pivot rod. The stop members are disclosed as retaining a button head provided on the end of the rod.
U.S. Pat. No. 254,739 to Wallis discloses a pitch chain including a pin with notches that include flattened surfaces. The reference discloses that in assembling the links together, each link is turned at a right angle so that the pin can be inserted. The reference further discloses that when the links are then returned to their operating position, the transverse displacement of the inserted pin is prevented.
The above described conveyor belts propose various methods for assembling a conveyor belt, and a variety of mechanisms for properly retaining a pivot rod. However, there still exists a need for conveyor belts that provide improved, alternative solutions for properly retaining the pivot rods of a conveyor belt. There also exists a need for conveyor belt construction where brick-laid modules is not required, and do not require links to have integrally molded, or mechanically attached module sections. Further, there also exists an unfulfilled need for providing of grid style conveyor belt that is more easily, and inexpensively, repaired, joined or separated in the field.